First choose the game difficulty, and then operate the role reasonably, shooting the crow that flies in the sky.
How to operate ？
A - GO LEFT
D - GO RIGHT
W - GO FORWARD
S - GO BACKWARD
SPACE - SHOOT
ESC - PAUSE GAME
UP - INCREASE GUNNING ANGLE
DOWN - REDUCE GUNNING ANGLE
LEFT- ROTATE ROLE TO LEFT
RIGHT- ROTATE ROLE TO RIGHT
Game difficulty
EASY — The birds fly very slowly
NORMAL — The birds fly at normal speed
HARD - The birds fly very fast
